Consistent Two to Four Degree Crystalloid Potassium Cardioplegia

_____________ _ The use of hypothermic crystalloid potassium cardioplegia in open heart surgery has been shown to be effective in arresting the heart and protecting it from ischemic injury during aortic crossclamping. A perfusion technique for the routine delivery of 2-4° centigrade (C) crystalloid potassium cardioplegia has been employed in 116 consecutive coronary artery bypass graft procedures between October 1980 and October 1981. The cardioplegic solution is infused with a low flow roller pump through a polyvinyl chloride tubing coil immersed in an ice bath which serves as the cooling device and a Sarns pediatric bubble trap. The planned initial dose of cardioplegia is 450 ml/m body surface area. With the initial cardioplegia infusion, the mean myocardial temperature was lowered to 14.4 ± 0.4°C (S.E.). Myocardial temperataure is maintained at less than 20°C at all times. A total of 2524 ± 73 ml of cardioplegia was administered for each patient with a mean crossclamp time of 83.6 ± 2.2 minutes and a total bypass time of 156 ± 3.6 minutes. CPK-MB and SGOT values were minimally elevated in the immediate postoperative period, but returned to normal on the second and third postoperative day respectively. Two patients in the study group died with an operative mortality of 1. 7 percent. The cardioplegia infusion system we have Address correspondence to: Benjamin Schneider, C.C.P., Division of Cardiovascular and Thoracic Surgery, University of Texas Medical Branch, Galveston, Texas 77550 Presented at the 20th International AmSECT Conference, Hollywood, Florida, April 25-28, 1982. Volume 14, Number 5, 1982 employed assured the delivery of crystalloid potassium cardioplegia to the myocardium at 2-4°C, provided continuous profound myocardial hypothermia, and resulted in good myocardial protection as determined by clinical variables followed postoperatively. Introduction _____________ _ The aim of cardioplegic arrest during aortic crossclamping is the intraoperative protection against myocardial damage with the preservation of the structure and function of the myocardium. The controversy surrounding what cardioplegic solution and which ingredients provide optimal protection has yet to be resolved. However, the cardioplegic method should combine the three basic mechanisms of myocardial protection that include: a) the conservation of intracellular energy stores by the induction of rapid diastolic arrest, b) a slowing of the metabolic processes through the use of hypothermia and c) the prevention and reversal of unfavorable ischemic changes1 • Hypothermic crystalloid potassium cardioplegia is currently the most widely used method of myocardial preservation during open heart surgery and has been shown to be effective in arresting the heart and protecting it from ischemic injury26 • Though the safe period of myocardial ischemia is not known, some have safely used hypothermic potassium cardioplegia for prolonged crossclamp times of up to three hours 7 • The use of multidose cardioplegic infusion with controlled infusion pressure and flow is considered the best available method of myocardial preThe Journal of Extra-Corporeal Technology 437 servation since it allows for the maintenance of profound myocardial cooling, continuous electromechanical arrest, and the washout of metabolic end products10 • Since clinical and experimental evidence indicate that optimal protection occurs when the myocardial temperature is maintained as low as is feasible • , our cardioplegic delivery system was designed to provide maximally cooled solution that can be infused in a totally controlled manner. The present study evaluated the efficacy of this method by which crystalloid potassium cardioplegia at 2-4° is used to induce arrest in a consecutive series of patients undergoing coronary artery bypass graft surgery. Materials and Methods, _______ _ One hundred and sixteen consecutive coronary artery bypass graft procedures between October 1980 and October 1981 were evaluated using a perfusion technique for the routine delivery of 2-4° crystalloid potassium cardioplegia. The cardioplegia solution contains 25 mEq/L of potassium adjusted to pH 7.8 and is hyperosmolar (See Figure 1). The planned initial dose of cardioplegia is 450 mVm2 • The cardioplegic solution was stored in a reservoira and administered with a low flow roller pumpb through a polyvinyl chloride tubing coilc (See Figure 2). The tubing coil is 31!6 inch internal diameter (I.D.) by 1/4 inch outer diameter (O.D.), POTASSIUM CARDIOPLEGIA-CONTENTS AND CHARACTERISTICS SODIUM POTASSIUM MAGNESIUM CHLORIDE ACETATE GLUCONATE CALCIUM DEXTROSE pH mOsm TEMPERATURE 137 mEq/L 25 mEq/L 6 mEq/L 101 mEq/L 26 mEq/L 23 mEq/L 1.35 mEq/L 5 g/L 7.8 330 2-4°C FIGURE 1. Potassium Cardioplegia-